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/*
* Copyright 2017, Google Inc.
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* http://www.apache.org/licenses/LICENSE-2.0
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.opencensus.implcore.trace.export;
import com.google.common.annotations.VisibleForTesting;
import io.opencensus.implcore.trace.SpanImpl;
import io.opencensus.trace.export.ExportComponent;
import io.opencensus.trace.export.SpanData;
import io.opencensus.trace.export.SpanExporter;
import java.util.ArrayList;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.annotation.concurrent.GuardedBy;
/** Implementation of the {@link SpanExporter}. */
public final class SpanExporterImpl extends SpanExporter {
private static final Logger logger = Logger.getLogger(ExportComponent.class.getName());
private final WorkerThread workerThread;
/**
* Constructs a {@code SpanExporterImpl} that exports the {@link SpanData} asynchronously.
*
* <p>Starts a separate thread that wakes up every {@code scheduleDelay} and exports any available
* spans data. If the number of buffered SpanData objects is greater than {@code bufferSize} then
* the thread wakes up sooner.
*
* @param bufferSize the size of the buffered span data.
* @param scheduleDelayMillis the maximum delay in milliseconds.
*/
static SpanExporterImpl create(int bufferSize, long scheduleDelayMillis) {
// TODO(bdrutu): Consider to add a shutdown hook to not avoid dropping data.
WorkerThread workerThread = new WorkerThread(bufferSize, scheduleDelayMillis);
workerThread.start();
return new SpanExporterImpl(workerThread);
}
/**
* Adds a Span to the exporting service.
*
* @param span the {@code Span} to be added.
*/
public void addSpan(SpanImpl span) {
workerThread.addSpan(span);
}
@Override
public void registerHandler(String name, Handler handler) {
workerThread.registerHandler(name, handler);
}
@Override
public void unregisterHandler(String name) {
workerThread.unregisterHandler(name);
}
private SpanExporterImpl(WorkerThread workerThread) {
this.workerThread = workerThread;
}
@VisibleForTesting
Thread getServiceExporterThread() {
return workerThread;
}
// Worker thread that batches multiple span data and calls the registered services to export
// that data.
//
// The map of registered handlers is implemented using ConcurrentHashMap ensuring full
// concurrency of retrievals and adjustable expected concurrency for updates. Retrievals
// reflect the results of the most recently completed update operations held upon their onset.
//
// The list of batched data is protected by an explicit monitor object which ensures full
// concurrency.
private static final class WorkerThread extends Thread {
private final Object monitor = new Object();
@GuardedBy("monitor")
private final List<SpanImpl> spans;
private final Map<String, Handler> serviceHandlers = new ConcurrentHashMap<String, Handler>();
private final int bufferSize;
private final long scheduleDelayMillis;
// See SpanExporterImpl#addSpan.
private void addSpan(SpanImpl span) {
synchronized (monitor) {
this.spans.add(span);
if (spans.size() > bufferSize) {
monitor.notifyAll();
}
}
}
// See SpanExporter#registerHandler.
private void registerHandler(String name, Handler serviceHandler) {
serviceHandlers.put(name, serviceHandler);
}
// See SpanExporter#unregisterHandler.
private void unregisterHandler(String name) {
serviceHandlers.remove(name);
}
// Exports the list of SpanData to all the ServiceHandlers.
private void onBatchExport(List<SpanData> spanDataList) {
// From the java documentation of the ConcurrentHashMap#entrySet():
// The view's iterator is a "weakly consistent" iterator that will never throw
// ConcurrentModificationException, and guarantees to traverse elements as they existed
// upon construction of the iterator, and may (but is not guaranteed to) reflect any
// modifications subsequent to construction.
for (Map.Entry<String, Handler> it : serviceHandlers.entrySet()) {
// In case of any exception thrown by the service handlers continue to run.
try {
it.getValue().export(spanDataList);
} catch (Throwable e) {
logger.log(Level.WARNING, "Exception thrown by the service export " + it.getKey(), e);
}
}
}
private WorkerThread(int bufferSize, long scheduleDelayMillis) {
spans = new LinkedList<SpanImpl>();
this.bufferSize = bufferSize;
this.scheduleDelayMillis = scheduleDelayMillis;
setDaemon(true);
setName("ExportComponent.ServiceExporterThread");
}
// Returns an unmodifiable list of all buffered spans data to ensure that any registered
// service handler cannot modify the list.
private static List<SpanData> fromSpanImplToSpanData(List<SpanImpl> spans) {
List<SpanData> spanDatas = new ArrayList<SpanData>(spans.size());
for (SpanImpl span : spans) {
spanDatas.add(span.toSpanData());
}
return Collections.unmodifiableList(spanDatas);
}
@Override
public void run() {
while (true) {
// Copy all the batched spans in a separate list to release the monitor lock asap to
// avoid blocking the producer thread.
List<SpanImpl> spansCopy;
synchronized (monitor) {
if (spans.size() < bufferSize) {
do {
// In the case of a spurious wakeup we export only if we have at least one span in
// the batch. It is acceptable because batching is a best effort mechanism here.
try {
monitor.wait(scheduleDelayMillis);
} catch (InterruptedException ie) {
// Preserve the interruption status as per guidance and stop doing any work.
Thread.currentThread().interrupt();
return;
}
} while (spans.isEmpty());
}
spansCopy = new ArrayList<SpanImpl>(spans);
spans.clear();
}
// Execute the batch export outside the synchronized to not block all producers.
final List<SpanData> spanDataList = fromSpanImplToSpanData(spansCopy);
if (!spanDataList.isEmpty()) {
onBatchExport(spanDataList);
}
}
}
}
}
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